The key to Margaret Thatcher is simplicity. By comparison with the Big Ten of English history, alongside whom she must surely be ranked, she was a straightforward person. Whereas King Alfred, Edward I, Henry V, Elizabeth, Cromwell, Chatham, William Pitt, Gladstone, Lloyd George and Churchill were all, in varying degrees, complex and many-sided people capable of surprising, confounding and shocking close admirers, Thatcher was simple, consistent and reliable.

A touch of the numinous: From left to right, Pope Benedict XVI, Paul Johnson and Lady Thatcher in May 2009.

Her moral character as a public woman was founded on plain, uncomplicated virtues. First, and most important, came courage, the essential basis of any great political career. I never knew her to flinch or retire in confusion. But she was quite capable of a tactical retreat from an untenable position. "The great thing is to learn how to fall back under fire," she said. I was surprised to hear her say: "I learned from Monty, never dig yourself deeper into a hole." She was the opposite of brash. Quite without bravado, her courage was pretty calm and cool on the whole. She liked to repeat Jack Kennedy's mot: "Don't get mad, get even." "The only wise thing I ever heard of him saying," she added. She said: "I never lost my temper with Arthur Scargill, like Ted Heath did. Losing my temper is a dreadful mistake. That's not the same as displaying anger, if necessary a terrible anger. You must be able to inspire fear. Winston used to walk up and down the Cabinet room saying of his colleagues: ‘I want them all to feel my power.' I know how he felt though I never quite said that."

Second came persistence. She said: "Flashes of courage are not enough. What matters is resolution. You must go on, and on, and on, and on, until people are sick and tired of your voice repeating the same thing." When she was right, Thatcher was never afraid of being a bore, and often was. She took the view that being boring was not a political vice. The essential thing was to be right. Once you were sure you were right, you had to hammer it home, as often and as firmly, as possible. "Hammer, hammer, hammer! That's a verb I like," she said.

Once, early in our acquaintance, I said to her: "Government spends money on all kinds of things, often rightly. But there are only three things it must do because nobody else can. External defence. Internal order. And maintaining an honest currency. The more extra things it tries to do, the more likely it is these three essentials will be done badly." Thatcher liked this so much she took a pencil and notebook out of her handbag and wrote it down. Years later, she suddenly began a harangue to me with: "Paul, there are three essential things a government must do . . ." I interrupted: "I told you that." "Really? I must have repeated that maxim hundreds of times. I like it. I normally quote my father. But then I suspect I often do when I find a saying I think useful, and true. I'll quote you in future. But then people might not take so much notice." "Oh, thanks very much."